This invention relates to a novel catalyst component to be employed with a cocatalyst for use in the polymerization of olefins to polyolefins such as polyethylene, polypropylene and copolymers such as ethylene copolymers with other alpha-olefins and diolefins. The catalyst is especially useful for the production of linear low density and high density polyethylenes, which catalyst component shows unusually high activity and excellent hydrogen response for the control of polymer molecular weight while obtaining improved comonomer response and improved bulk density of produced polymer product. The polymer product obtained evidences an important balance of polymer properties, for example, the catalyst system obtains a polymer with a high bulk density, narrow molecular weight distribution, an improved balance in polymer product machine direction tear strength and transverse direction tear strength. As a result, blown film produced from polymer products such as linear low density polyethylene manifests an overall higher strength.
The catalyst component comprises a prepolymerized solid reaction product obtained by contacting a solid, particulate, porous support material such as, for example, silica, alumina, magnesia or mixtures thereof, for example, silica-alumina, in stages with an organometallic composition treated with an oxygen containing compound, an acyl halide, a transition metal compound, a Group IIIa metal hydrocarbyl dihalide and prepolymerizing the solid product with ethylene to form a prepolymerized transition metal catalyst component. The novel catalyst component, which when used with an aluminum alkyl cocatalyst, provides the novel catalyst system of this invention which can be usefully employed for the polymerization of olefins.
The catalyst system can be employed in slurry, single-phase melt, solution and gas-phase polymerization processes and is particularly effective for the production of linear polyethylenes such as high density polyethylene.
Recently, interest has arisen in the use of magnesium-titanium complex catalyst components for the polymerization of olefins. For example, European Patent Application No. 27733, published Apr. 29, 1981 discloses a catalyst component obtained by reducing a transition metal compound with an excess of organomagnesium compound in the presence of a support such as silica and thereafter deactivating the excess organomagnesium compound with certain deactivators including hydrogen chloride.
U.S. Pat. No. 4,136,058 discloses a catalyst component comprising an organomagnesium compound and a transition metal halide compound, which catalyst component is thereafter deactivated with a deactivating agent such as hydrogen chloride. This patent does not teach the use of support material such as silica but otherwise the disclosure is similar to the above-discussed European patent application.
U.S. Pat. No. 4,250,288 discloses a catalyst which is the reaction product of a transition metal compound, an organomagnesium component and an active non-metallic halide such as HCl and organic halides containing a labile halogen. The catalyst reaction product also contains some aluminum alkyls.
Catalyst components comprising the reaction product of an aluminum alkyl-magnesium alkyl complex plus titanium halide are disclosed in U.S. Pat. No. 4,004,071 and U.S. Pat. No. 4,276,191.
U.S. Pat. No. 4,173,547 and U.S. Pat. No. 4,263,171, respectively disclose a catalyst component comprising silica, an organoaluminum compound, titanium tetrachloride and dibutyl magnesium and a catalyst component comprising a magnesium alkyl-aluminum alkyl complex plus titanium halide on a silica support.
Each of U.S. Pat. Nos. 4,402,861, 4,378,304, 4,388,220, 4,301,029 and 4,385,161 disclose supported catalyst systems comprising an oxide support such as silica, an organomagnesium compound, a transition metal compound and one or more catalyst component modifiers. These patents do not disclose the catalysts of this invention.
In British Pat. No. 2,101,610 silica is treated with a magnesium alkyl, an alcohol, benzoyl chloride and TiCl.sub.4. In each of Japanese Kokai Nos. 50-098206 and 57-070107 acyl halides are employed during the preparation of titanium supported catalysts.
The catalyst systems comprising magnesium alkyls and titanium compounds, although useful for the polymerization of olefins such as ethylene and other 1-olefins, often do not show excellent responsiveness to hydrogen during the polymerization reaction for the control of molecular weight, do not show an extremely high catalytic activity and obtain polymer product manifesting poor bulk density and film properties.
Prepolymerization of Ziegler-type catalysts are illustrated in British Pat. No. 1,300,734, U.S. Pat. No. 3,404,096, U.S. Pat. No. 3,689,597 and U.S. Pat. No. 4,177,160. These patents do not disclose improving polymer bulk density by way of prepolymerizing a supported catalyst with a minor amount of ethylene.
In U.S. Pat. No. 4,451,574 issued May 29, 1984 a catalyst system obtained by treating an inert particulate support, such as silica, with an organometallic compound such as a magnesium alkyl, a titanium halide and a halogen gas is disclosed. Although the catalyst obtains very high activities, there is a need for improving the film properties of polymer product obtained by polymerizing olefins in the presence of the catalyst and to improve the bulk density of polymer product.
In my cofiled application Ser. No. 638,168, filed Aug. 6, 1984, now U.S. Pat. No. 4,558,025 there is disclosed a titanium containing catalyst component obtained by treating an inert particulate support such as silica with the reaction product of magnesium dialkyl and an alcohol, an acyl halide, a transition metal compound such as titanium tetrachloride and a Group IIIa metal alkyl dihalide.
In accordance with this invention catalyst combinations have been found which have extremely high catalytic activities and excellent hydrogen responsiveness for the control of molecular weight and obtain polymer product with greatly improved film properties and bulk density. The resins exhibit excellent melt strength with a surprising decrease in power consumption hence an increase in extrusion rates, excellent MD tear strength and dart impact strength.
The new catalyst systems and catalyst component of this invention are obtained by contacting an organometallic compound, an alcohol, an acyl halide, a transition metal compound and a Group IIIa metal hydrocarbyl dihalide in the presence of an oxide support and prepolymerizing with a minor amount of ethylene. The catalyst system employing the transition metal containing catalyst component is advantageously employed in a gas phase ethylene polymerization process since there is a significant decrease in reactor fouling as generally compared with catalytic prior art ethylene gas phase polymerization processes thereby resulting in less frequent reactor shut downs for cleaning.